Art of manufacturing metal articles by cold-drawing.



R. .l. SHOEMAKER. ART OF MANUFACTURING METAL ARTICLES BY COLD DRAWING.

APPLICATION FILED OCT. 3. 1918.

Patented Dec. 23, 1919.

nonnn'r JAY snonnaiznn, or MILWAUKEE, WISCONSIN.

'ABT OF MANUFACTURING- METAL' ARTICLES BY COLD- DRAWTNG.

To all whom it may concern.-

.Be it known that I ROBERT J. SnonMAKnn', 1 a citizen of the Umted States,'residing at. Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in the Art of.

Manufacturing Metal Articles by Cold- ]Drawing, of which the following is a specification. 1

My invention relates to the manufacture of cold drawn metal articles such; for ex-. ample, as seamless steel tubes, and the primary objects of the invention are: to providea simple, economical and eifectlve method of manufacturing tubes or, other articles having highly polished surfaces which will be proof against rust, corrosion or scale; to facilitate and cheapen the manufacture of cold drawn metal articles by obtaining a greater reduction for each pass than has been possible with methodsheretofore used; to reduce the wear on dies and mandrels employed in' the drawing operation; to eliminate the usual annealing, pickling and lubricating of the tube between passes; to provide a method whereby the tubes will be more truly circular in cross section and will have amore uniform wallthickness and whereby the tubes, if desired, may be rawn to a smaller gage than has heretofore been possible; to economize labor and material by minimizing the number of broken, scratched or otherwise defective tubes to a minimum; and to provide other an incidental improvements in the manufacture of cold drawn metal articles as will appear from the following description of {a mic -f jlpreferred method of practising the 1 :3. Thefin vention consists in subjecting the billet before it is drawn to certain treatment. whereby its reduction to the finished article, by successive drawing operations, is facilitated and whereby the finished article itself will have thedesirable characteristics above noted. The drawing may be performed by means of apparatus commonly used for cold drawing operations. An apparatus' of this type is shown, somewhat diagrammatically, in the annexed drawing in which Fi ml is a view, in elevation, showing the ie block and-die in section, of an apparatus or draw bench for drawing seamless steel tubes.

Specification of Letters latent. Application flied October 3, 1918. Serial No. 256,692.

, I improve Patented Dec. 23, 1919.

f Fig. 2 is a sectional view on line 2-2 of iccording' to the ordinary methods of manufacture, the billet, after being pierced and reduced to proper dimension in the rollin mill, is pointed at one end, pickled m a llute and to remove scale, covered or f doped with a lubricant, and drawn I through the die 10 over a mandrel 11. The

pointed end of the billet is gripped between jaws 12 on a carriage 13 wh1ch oper-- ates over. a table 14. The carriage has a hook 15 that may be engaged with a link belt 16 which extends around a sprocket 17 and is driven by any suitable means. The

mandrel 11' extends through the billet,

to the tail stock 19. -As the carriage 13 moves away from the die, which is set in a die block 20, the tube is drawn'through the die and reduced, as indicated at 21.

The drawin operation is repeated through dies an over mandrels of progressively small diameter until the article is reduced to the desired diameter and wall thickness. Between each pass it has heretofore been necessary to anneal the tube, the surfaces of which are made excessively hard by contact with the dies and mandrels. After annealing the billet hasto be pickled each time to remove scale and doped with the lubricant. sume a great deal of time, involve the use of more or less costly acids and greases, and re uire a repeated'handling of the billets.

en all precautions-are taken a considerablev percentage of the tubes are either broken during the drawing operations "or so scratched b the dies and mandrels asto be defective. .he dies are soon worn and re quire frequent replacement.

u on this method as follows: The billets a er the are pointed and pickled are plated insi e and out with lead, preferably by the method described in the shown in the drawing at 18, and is anchored These operations conpatent to McClintock and Shoemaker No.

an improvement upon the patented methods above referred to. In the application just referred to the flux employed consists of ap proximately 80% of zinc chlorid, 15% of common salt and 5% of tin chlorid.

In accordance with the plating operation above described, the articles are passed into a bath of the molten plating metal, through a body of the flux which is caused to float on the plating metal. The billets, when Withdrawn from the plating bath, are ready for drawing. It is not necessary to dope them with the usual lubricant. The coating or plating of lead performs the function of a lubricant during the drawing operation and performs it much more satisfactorily than the lubricating compounds heretofore used. Furthermore, the plating is not scraped off by contact with the die and mandrel, at least to any appreciable extent. It.remains on the billet and protects the steel of the billet from becoming superficially hardened as under the old method. The usual steps of annealing and pickling of the billet between successive passes are also entirely eliminated. The saving of material, time and labor is very considerable. Furthermore, a greater reduction can be made at each pass than has been heretofore possible. The tubes may also be drawn to a lighter gage, when desired, and with tubes drawn to the same gage the percentage of defective tubes, due to breakage in drawing or scratching by the dies, is considerably reduced.

In the finished article both inner and outer surfaces are highly polished. The lead plating remains intact and, in fact, the pressure of the plated surfacesagainst the die and mandrel tends to all the more firmly unite the plating metal to the tube and give the plated surfaces a high and perfect finish free from pin holes or other defects. Tubes of this character may be advantageously used as boiler tubes or in other situatlons where ordinary steel pipes are liable to rust, corrosion or scale. If an annealed tube is required the heating and cooling should be done in a reducing atmosphere as the annealing process will otherwise oxidize the lead coating. After the tube is annealed 1t may be given a very light pass through the draw bench to restore the original high polish and luster of the plated surfaces.

I sometimes prefer, in drawing a very light Walled tube, for example, a twenty-four or twenty-six gage tube, which requires eight or more passes from the original billet, to plate the tube a second time with lead before making the finishing passes. This is usually done in case of an eight-pass tube at the end of the fifth pass. In this way a line polish and a high degree of finish are secured.

In the case of a boiler tube requiring an extra heavy lead coating, I may draw the tube without a lead coating, using for a lubricant ordinary grease or dope, to within one-sixteenth of an inch of the required size. The tube is annealed, pickled, lead plated and then finished with a light pass through the draw bench.

A tube of this kind, although preserving the bright finish and high polish of an un annealed tube, 'may be flattened, swaged or beaded without failure. Further annealing is not necessary. By the term lead I intend to include alloys of lead containing a very small percentage of tin or other alloying metal, say, from two to four per cent. as mentioned in the patents above referred to.

I claim:

1. Method of manufacturing metal articles by cold drawing which consists in immersing the billet in molten lead through a supernatant flux containing Zinc chlorid as its principal ingredient, and then drawing the article to the desired cross sectional configuration.

2. Method of manufacturing cold drawn articles which consists in immersing the billet in molten lead through a supernatant flux containing Zinc chlorid as its principal ingredient, and then giving the billet several passes through the draw bench without treatment between passes to reduce it to the desired cross sectional configuration.

3. Improvement in the method of manufacturing articles by cold drawing which consists in plating the billet with a relatively soft metal, subjecting the same to a drawing operation, annealing the article in a reducing atmosphere, and then giving the article a light pass through the draw bench to re-- store the original luster and finish of the plating.

4:. Method of manufacturing seamless steel tubes which comprises immersing the billet in a bath of lead in a molten state through a supernatant flux containing Zinc chlorid as its principal ingredient, then drawing the billet, without treatment between passes. through dies and corresponding mandrelsot progressively smaller diameter to reduce it to a tube of the desired cross sectional configuration.

ROBERT JAY SHOEMAKER. 

